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If a tomato plant has ragged holes, stripped leaves or dark droppings, look closely through its foliage for a large green caterpillar with a horn-like projection at its rear. Hand-picking is often enough in a home garden. If you find white, rice-like cocoons on a hornworm, leave it on the plant where practical: those are beneficial parasitoid wasps, not eggs to remove.
How to identify a tomato hornworm
The tomato hornworm is the caterpillar of Manduca quinquemaculata. It is green, has pale diagonal markings along its body and a horn-like projection at the rear. It can grow several inches long, but size and green color alone are not enough for identification: check its markings, rear horn, the plant it is on and the pattern of damage.
The tobacco hornworm (Manduca sexta) is a close lookalike that also feeds on tomato. The two species can be difficult to distinguish, but the practical controls for a home garden are much the same.
Look for feeding signs and frass
- Large, ragged holes in leaves, or leaves and stems that have been stripped.
- Dark, blocky droppings (frass) on leaves or on the ground beneath the plant.
- Damage to immature fruit in some cases.
Hornworms blend into green foliage, so frass and fresh feeding damage can be easier to spot than the caterpillar itself.
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- Protect your oasis with Captain Jack's Bt Thuricide Ready-to-Use Spray; this product controls cabbage looper, hornworms, tent caterpillars and more
- Protects fruits, vegetables, shade trees and ornamentals; designed for use on broccoli, cauliflower, kale, mustard greens, eggplant, pepper, melons, tomatoes, cabbage, and more
- Kills worms and caterpillar stage insects while causing no harm to birds, earthworms, or beneficial insects, such as honeybees and ladybugs; this product kills by ingestion, after ingesting, bugs immediately stop feeding and will die within 2-3 days
- Active ingredient of the product is a strain of the bacterium bacillus thuringiensis, which is a leading insecticide used worldwide; approved for organic gardening
- This product arrives conveniently ready-to-use in a trigger sprayer bottle; to use, apply thoroughly to affected plants when worms or caterpillars are first noticed; for full use instructions please see product label
How to find hornworms on tomato plants
Inspect plants regularly rather than waiting for extensive damage. Check leaf undersides and the interior of the canopy, and look for eggs, caterpillars, fresh feeding and frass. Regular searches can help you find an infestation while it is still manageable.
- Look first for fresh holes, stripped foliage and dark frass on the plant and soil below it.
- Trace the signs upward and inspect nearby leaves, including their undersides and the shaded interior of the plant.
- If you still cannot find the caterpillar, gently agitate the foliage or spray water on the plant to make it move.
- For an optional night search, use a UV or black light to help spot caterpillars. It is a detection aid, not a requirement.
How to remove hornworms
For a home garden, hand-picking caterpillars and removing egg patches are effective controls; hand-picking often provides satisfactory control. Check the caterpillar for white cocoons before removing it.
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- Thuricide BT Caterpillar Control concentrate is used by organic gardeners and is made from bacteria that is toxic to listed pests.
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If there are no white cocoons
Remove the caterpillar and destroy it. One disposal method suggested by Maryland Extension is to drop it into soapy water. Choose a method appropriate to your garden and follow local guidance; do not assume a pesticide or particular disposal method is necessary for every situation.
If there are white, rice-like cocoons
These are cocoons of parasitoid wasps, not a row of eggs. The wasp larvae develop on or within the hornworm and later emerge. Leave the parasitized caterpillar on the plant where practical: it is being suppressed, helps sustain beneficial wasps and will stop feeding and eventually die.
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- INSECT KILLER - This pest control is designed for use on caterpillars and worm type insects, such as cabbage looper, bagworm, gypsy moth, fall cankerworm, elm spanworm and many more.
- FOLIAGE PROTECTOR - This insecticide is designed for use on a variety of plants including broccoli, celery, cabbage, turnip greens, mustard greens, cauliflower, melons, lettuce, tomatoes, shade trees, ornamentals and many more.
- SAFE FOR EARTHWORMS & BEES - When used as directed, Monterey B.t. has no effect on birds, earthworms, or beneficial insects such as honeybees or ladybugs.
- FOR ORGANIC GARDENING - OMRI Listed for Organic Gardening. Organic Material Review Institute reviews products to ensure a product complies with all organic standards under the USDA’s National Organic Program (NOP)
- EASY TO APPLY - Product instantly mixes with water and should be applied using either a trigger spray bottle or pressure tank sprayer. Carefully read and use according to label directions.
When to use Bt—and what to check first
Bacillus thuringiensis (Bt) is an optional biological control for actively feeding caterpillars. A hornworm must eat treated foliage for Bt to work; it is not a contact treatment. Rain or irrigation can wash the product off, so repeat applications may be needed as directed on the product label.
- Check that the specific product label lists tomatoes and the intended use.
- Follow the full label for the formulation, crop, application timing and location. Rates and directions are product-specific; do not transfer instructions from one product to another.
- Do not assume a universal application schedule. Weather, product directions and local requirements matter.
Use selective controls where possible to preserve beneficial insects. Maryland Extension notes that hornworm damage rarely warrants insecticide in a home garden.
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Which control fits your garden?
| Approach | When it fits | Trade-off |
|---|---|---|
| Inspect and hand-pick | Routine checks or a small number of caterpillars. | Requires finding the hornworms, but acts immediately and avoids broad pesticide exposure. |
| Leave a cocoon-covered hornworm | White, rice-like parasitoid wasp cocoons are present. | Leaves the caterpillar in place temporarily while natural enemies suppress it. |
| Bt on foliage | Actively feeding caterpillars, when a product label permits use on tomatoes. | The caterpillar must eat treated foliage; rain or irrigation may wash treatment away, and label-directed repeat applications may be needed. |
| Seasonal tillage | A locally appropriate preventive step in spring or fall. | It targets overwintering pupae, not feeding caterpillars currently on the plant, and results vary. |
Can tilling help prevent hornworms?
In some places, tilling soil in spring or fall may expose or kill overwintering pupae. Illinois Extension reports that tillage has destroyed up to 90% of overwintering pupae. That is a reported upper figure, not a guaranteed result for a particular garden; whether tillage is useful depends on local conditions and timing.
Quick Recap
Best Value
- Protect your oasis with Captain Jack's Bt Thuricide Concentrate; this product controls cabbage looper, hornworms, tent caterpillars and more
- Protects fruits, vegetables, shade trees and ornamentals; designed for use on broccoli, cauliflower, kale, mustard greens, eggplant, pepper, melons, tomatoes, cabbage, and more
- Kills worms and caterpillar stage insects while causing no harm to birds, earthworms, or beneficial insects, such as honeybees and ladybugs; this product kills by ingestion, after ingesting, bugs immediately stop feeding and will die within 2-3 days
- Active ingredient of the product is a strain of the bacterium bacillus thuringiensis, which is a leading insecticide used worldwide; approved for organic gardening
- This product arrives conveniently ready-to-mix with water; to use, mix with water according to label instructions and apply thoroughly to affected plants when worms or caterpillars are first noticed; for full use instructions please see product label
A simple monitoring routine
- Check tomato plants regularly for eggs, fresh feeding, frass and caterpillars.
- Inspect leaf undersides and dense growth, where green caterpillars can be hard to see.
- Remove caterpillars without cocoons and egg patches; leave cocoon-covered hornworms where practical.
- If choosing Bt, verify the individual product label and recheck plants after treatment, especially following rain or irrigation.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
